Superabsorbent polymers with improved odor control capacity and process for the production thereof

ABSTRACT

The present invention relates to a water-absorbing polymer and to a process for preparation, including finishing the water-absorbing polymer, with 0.0001 to 3% by weight, of a peroxo compound, based on the acrylic acid, after the polymerization is treated, and to a process for producing a hydrogel polymer, to the product of the process and to use.

This application claims priority to U.S. Ser. No. 61/948,114, filed 5Mar. 2014 and the European Application No. EP14157784.1 filed 5 Mar.2014, the disclosures of which are expressly incorporated herein byreference.

FIELD

The present invention relates to superabsorbent polymers with improvedodor control capacity, and to processes for the production thereof.

BACKGROUND

DE 40 20 780 C1 (U.S. Pat. No. 5,409,771 A) discloses the post-treatmentof superabsorbent polymers by post-crosslinking the surfaces of thepolymer particles. The post-crosslinking of the surface of thewater-absorbing polymer particles particularly increases the absorptioncapacity of the polymer particles under pressure.

DE 199 09 653 A1 (US 2003/207997 A1) and DE 199 09 838 A1 (U.S. Pat. No.6,605,673 B1) describe pulverulent, surface post-cross-linked polymerswhich absorb water, aqueous or serous fluids or blood, which are basedon monomers bearing acid groups and which have been coated andpost-cross-linked with a surface post-crosslinker and a cation inaqueous solution. The polymers disclosed in this prior art haveadvantageous absorption properties compared to conventional polymers,especially a high permeability.

Hygiene articles such as diapers and incontinent pads, liners andarticles containing superabsorbent polymers are designed to absorbbodily fluids such as urine. Urine can generally be a source of twomajor types of nuisance malodors; one from the bacterial or enzymaticdecomposition of urea to form ammonia; the second from organic moleculesfound in the urine itself. The first odor requires time to develop, i.e.time for the urea to decompose to ammonia, depending on many factorssuch as the bacteria present on the skin, the pH, the temperature, amongothers. Odor from organic molecules, usually the byproducts of digestionor other metabolic processes, on the other hand, is present immediatelywhen the urine is excreted from the body. There is a need for a means ofcontrolling, reducing or even eliminating both types of odor.

In the case of prolonged wearing of hygiene articles including absorbentpolymers, especially when some of these have already absorbed bodyfluids such as urine, the organic constituents of the urine and the bodyheat of the wearer can soon cause an unpleasant odor nuisance. In orderto counter this, numerous attempts have been made through appropriateadditions in the non-superabsorbent constituents of the hygiene articleto achieve binding of the odor-forming substances or to mask the odor bymeans of perfume or the like. The introduction of such substances in theform of non-superabsorbent constituents often has an adverse effect onthe performance of these hygiene articles during wear. For instance, theodor-inhibiting or odor-reducing substances, which are at firstspatially separate from the superabsorbent region, may be brought intothe region which contains superabsorbent by the introduction of bodilyfluids, for example by a washing action, odor where they then exhibit anadverse effect overall on the performance of the superabsorbent andhence of the hygiene article. A further disadvantage of this concept isthat the majority of the body fluid released into the hygiene article isin any case present within the superabsorbent, and the odor-inhibitingor odor-reducing substances present outside the superabsorbent aretherefore less able to display their effect.

DE 198 25 486 (US 2004/157989 A1) and DE 199 39 662 A1 (US 2003/157318A1) disclose the combination of superabsorbents with cyclodextrin forodor reduction. However, it can be inferred from this approach, which isindeed promising, that the cyclodextrin exhibits its odor-inhibitingaction in the superabsorbent only under particular conditions, namelywhen it is ensured that the cyclodextrin does not separate again fromthe superabsorbent. It is preferable in this context that thecyclodextrin is incorporated at least into the surface of thesuperabsorbent article, by virtue of cyclodextrin and/or cyclodextrinderivatives being covalently and/or ionically bonded and/or incorporatedtherein.

DE 103 34 271 (US 2007/015860 A1) further discloses superabsorbentagglomerates which may have a multitude of odor binders in homogeneousform in the agglomerate. However, this document, which discloses anexcellent solution for the use of fine superabsorbent particles, doesnot provide superabsorbents having odor-binding properties which are ofparticularly good suitability for use in hygiene articles. Thus, as wellas an efficient and effective use of the odor binders, thesuperabsorbent properties influenced by this odor binders are also stillin need of improvement.

DE-A-10 2005 055 497 (US 2010/035757 A1) teaches imparting improvedodor-binding properties to superabsorbent polymers by contacting withmetal salts of ricinoleic acid and/or with amino acids.

Other approaches such as the use of lower pH additives, enzymeinhibitors, chelants and the like, are only effective in delaying theformation of ammonia from urea and have little effect on organicmolecule odor, or only address a small fraction of the types of organicodor. One of the difficulties with controlling, reducing or eliminatingorganic odor is the large variety of chemistries of the organic malodormolecules, including ketones and aldehydes, amines, mercaptans,sulfides, cyclic compounds, unsaturated compounds and aromatics and thelike. Only addressing one or two classes of organic odor does little toreduce the overall nuisance created by urine malodors.

SUMMARY

In general terms, the problem addressed by the present invention wasthat of alleviating or even overcoming the disadvantages arising fromthe prior art.

One problem addressed by the invention was that of providing awater-absorbing polymer which firstly possesses good odor-binding and/or-reducing properties. Secondly, there is a need for a water-absorbingpolymer with multiple odor control, that is to say, the ability toreduce or eliminate odors from ammonia and organic molecules. Third, theorganic odor control must be effective on a wide range of organicmolecule odors, not just one or two chemical classes. At the same time,it is to be ensured that the performance of the hygiene articleincluding this odor-binding and -reducing water-absorbing polymer isessentially just as good as or even better than the performance of thehygiene article comprising a superabsorbent which odor does not includethe odor binder. More particularly, the performance properties of thewater-absorbing polymer were to be influenced to a minimum degree or atmost slightly by the use of odor-binding additives, which are to be usedin minimum amounts. Advantageously, the performance properties of thewater-absorbing polymer are in some cases actually to be improved by theaddition of the odor-binding or -reducing additive.

In addition, the water-absorbing polymer, on contact with aqueous bodyfluids, more particularly with urine or iron-containing fluids, forexample blood or menstrual fluids, was to have a minimum tendency tosevere discoloration.

Furthermore, a problem addressed by the invention was that of providinga process by which such a water-absorbing polymer can be obtained.Moreover, a problem addressed by the invention was that of providing ahygiene article which, as well as good odor-binding and odor-reducingproperties for the multiple sources of urine malodors, also exhibitsgood absorption performance. Another problem addressed by the presentinvention was that of providing water-absorbing polymers which cangenerally be incorporated into composites or else can be used as acomposite or as such in chemical products or constituents thereof.

These objects are achieved by the subject-matter of the independentclaims. Advantageous configurations and developments which can occurindividually or in combination form the subject-matter of the dependentclaims in each case.

DETAILED DESCRIPTION

A contribution to the solution of the problem stated at the outset ismade by an inventive water-absorbing polymer comprising:

-   (α1) 20-99.999% by weight, preferably 55-98.99% by weight and more    preferably 70-98.79% by weight of polymerized, ethylenically    unsaturated monomers bearing acid groups, or salts thereof, or    polymerized, ethylenically unsaturated monomers including a    protonated or quaternized nitrogen, or mixtures thereof, particular    preference being given to mixtures including at least ethylenically    unsaturated monomers containing acid groups, preferably acrylic    acid,-   (α2) 0-80% by weight, preferably 0-44.99% by weight and more    preferably 0.1-44.89% by weight of polymerized, monoethylenically    unsaturated monomers copolymerizable with (α1),-   (α3) 0.001-5% by weight, preferably 0.01-3% by weight and more    preferably 0.01-2.5% by weight of one or more crosslinkers,-   (α4) 0-30% by weight, preferably 0-5% by weight and more preferably    0.1-5% by weight of a water-soluble polymer,-   (α5) 0-20% by weight, preferably 2.5-15% by weight and more    preferably 5-10% by weight of water, and-   (α6) 0-20% by weight, preferably 0-10% by weight and more preferably    0.1-8% by weight of one or more additives, where the sum of the    weights of (α1) to (α6) is 100% by weight,    wherein    the water-absorbing polymer has been treated with 0.0001 to 3% by    weight, preferably 0.0002 to 2% by weight and more preferably 0.0007    to 1.8% by weight of a peroxo compound, based on the acrylic acid,    after the polymerization. Preferred are water-absorbing polymers    with 0.0001 to 1.5% by weight of a peroxo compound, based on the    acrylic acid, added after the polymerization.

Peroxo compounds in the context of the present inventions are understoodto mean those from the group of organic and inorganic peroxo compounds.

In the context of the present invention, the term “inorganic peroxocompounds” is preferably understood to mean those from the group ofalkali metal or alkaline earth metal peroxomonosulphate, orperoxodisulphate. The inorganic peroxo compounds selected are preferablythose from the group of alkali metal or alkaline earth metalperoxomonosulphate, or peroxodisulphate, sulpho monoperacid,peroxomonosulphate triple salt (Caro's acid), most preferablyperoxomonosulphate triple salt.

In the context of the present invention, the term “organic peroxocompounds” is preferably understood to mean those from the group ofcarbamide peroxo, peroxocarboxylic acids, more preferablyperoxocarboxylic acids.

Water-absorbing polymers which have been treated with the above listedperoxo compounds possess excellent odor-binding and -reducing propertiesfor both ammonia-type and organic-type odors. The performance of thehygiene article including the “peroxo compound treated” water-absorbingpolymer is in many cases as good as or even better than the performanceof the hygiene article comprising a superabsorbent without the peroxocompounds. Surprisingly, even discoloration is not severe in the “peroxocompound treated” water-absorbing polymers. Best results are achievedwith the inorganic peroxo compounds which are therefore preferredaccording to the invention. Especially inorganic peroxo compounds fromthe group of alkali metal or alkaline earth metal peroxomonosulphate, orperoxodisulphate, sulpho monoperacid and most of all peroxomonosulphatetriple salt (Caro's acid), added in the before described and preferredweight % ranges, resulted in water-absorbing polymers with excellentodor-binding properties.

Inorganic peroxo Salts involve metals from the group of the alkalimetals, alkaline earth metals and the boron group. Preference is givenhere to the metals from the group of sodium, potassium, caesium,rubidium, magnesium, calcium, strontium, barium, aluminum, gallium,indium. Particular preference is given to those from the group ofsodium, potassium, calcium, magnesium, and optionally mixtures of these.Particular preference is given to metals from the group of sodium,potassium, calcium and magnesium.

In this context, water-absorbing polymer structures preferred inaccordance with the invention are especially fibers, foams or particles,fibers and particles being particularly preferred and particles mostpreferred.

The dimensions of polymer fibers preferred in accordance with theinvention are such that they can be incorporated into or as yarns fortextiles, and also directly into textiles. It is preferable inaccordance with the invention that the polymer fibers have a length inthe range from 1 to 500 mm, preferably 2 to 500 mm and more preferably 5to 100 mm, and a diameter in the range from 1 to 200 denier, preferablyfrom 3 to 100 denier, and more preferably from 5 to 60 denier.

The dimensions of polymer particles preferred in accordance with theinvention are such that they have a mean particle size to ERT 420.2-02in the range from 10 to 3000 μm, preferably from 20 to 2000 μm and morepreferably from 150 to 850 μm or from 150 to 600 μm. In this context, itis especially preferable that the proportion of the polymer particleshaving a particle size within a range from 300 to 600 μm is at least 30%by weight, more preferably at least 40% by weight, further preferably atleast 50% by weight and most preferably at least 75% by weight, based onthe total weight of the water-absorbing polymer particles. In anotherembodiment of the inventive water-absorbing polymer structure, theproportion of the polymer particles having a particle size within arange from 150 to 850 μm is at least 50% by weight, more preferably atleast 75% by weight, further preferably at least 90% by weight and mostpreferably at least 95% by weight, based on the total weight of thewater-absorbing polymer particles.

The monoethylenically unsaturated monomers (α1) containing acid groupsmay be partly or fully neutralized, preferably partly. Themonoethylenically unsaturated monomers containing acid groups havepreferably been neutralized to an extent of at least 10 mol %, morepreferably to an extent of at least from 25 to 50 mol % and furtherpreferably to an extent of from 50 to 90 mol %. The neutralization ofthe monomers (α1) may precede or else follow the polymerization. In thiscase, the partial neutralization is effected to an extent of at least 10mol %, more preferably to an extent of at least from 25 to 50 mol % andfurther preferably to an extent of 50 to 90 mol %. Moreover,neutralization can be effected with alkali metal hydroxides, alkalineearth metal hydroxides, ammonia, and carbonates and bicarbonates. Inaddition, any further base which forms a water-soluble salt with theacid is conceivable. Mixed neutralization with different bases is alsoconceivable. Preference is given to neutralization with ammonia or withalkali metal hydroxides, more preferably with sodium hydroxide or withammonia.

In addition, the free acid groups in a polymer may predominate, suchthat this polymer has a pH within the acidic range. This acidicwater-absorbing polymer may be at least partly neutralized by a polymerwith free basic groups, preferably amine groups, which is basic comparedto the acid polymer. These polymers are referred to in the literature as“Mixed-Bed Ion-Exchange Absorbent Polymers” (MBIEA polymers) and aredisclosed in WO 99/34843 inter alia. The disclosure of WO 99/34843 ishereby incorporated by reference and is thus considered to form part ofthe disclosure. In general, MBIEA polymers constitute a compositionwhich includes firstly basic polymers capable of exchanging anions, andsecondly a polymer which is acidic compared to the basic polymer and iscapable of exchanging cations. The basic polymer has basic groups and istypically obtained by the polymerization of monomers which bear basicgroups or groups which can be converted to basic groups. These monomersare in particular those which have primary, secondary or tertiary aminesor the corresponding phosphines, or at least two functional groups. Thisgroup of monomers includes especially ethyleneamine, allylamine,diallylamine, 4-aminobutene, alkyloxycyclines, vinylformamide,5-aminopentene, carbodiimide, formaldacine, melamine and the like, andthe secondary or tertiary amine derivatives thereof.

Preferred monoethylenically unsaturated monomers (α1) containing acidgroups are acrylic acid, methacrylic acid, ethacrylic acid,α-chloroacrylic acid, α-cyanoacrylic acid, β-methylacrylic acid(crotonic acid), α-phenylacrylic acid, β-acryloyloxypropionic acid,sorbic acid, α-chlorosorbic acid, 2′-methylisocrotonic acid, cinnamicacid, p-chlorocinnamic acid, β-stearyl acid, itaconic acid, citraconicacid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid,fumaric acid, tricarboxyethylene and maleic anhydride, preference beinggiven particularly to acrylic acid and methacrylic acid with acrylicacid being especially preferred.

In addition to these monomers containing carboxylate groups, preferredmonoethylenically unsaturated monomers (α1) containing acid groupsadditionally include ethylenically unsaturated sulphonic acid monomersor ethylenically unsaturated phosphonic acid monomers.

Preferred ethylenically unsaturated sulphonic acid monomers areallylsulphonic acid or aliphatic or aromatic vinylsulphonic acids oracrylic or methacrylic sulphonic acids. Preferred aliphatic or aromaticvinylsulphonic acids are vinylsulphonic acid, 4-vinylbenzylsulphonicacid, vinyltoluenesulphonic acid and styrenesulphonic acid. Preferredacryloyl- or methacryloylsulphonic acids are sulphoethyl(meth)acrylate,sulphopropyl(meth)acrylate, 2-hydroxy-3-methacryloyloxypropylsulphonicacid, and (meth)acrylamidoalkylsulphonic acids such as2-acrylamido-2-methylpropanesulphonic acid.

Preferred ethylenically unsaturated phosphonic acid monomers arevinylphosphonic acid, allylphosphonic acid, vinylbenzylphosphonic acid,(meth)acrylamidoalkylphosphonic acids, acrylamidoalkyldiphosphonicacids, phosphonomethylated vinylamines and (meth)acryloylphosphonic acidderivatives.

Preferred ethylenically unsaturated monomers (α1) containing aprotonated nitrogen are preferably dialkylaminoalkyl(meth)acrylates inprotonated form, for example dimethylaminoethyl(meth)acrylatehydrochloride or dimethylaminoethyl(meth)acrylate hydrosulphate, anddialkylaminoalkyl(meth)acrylamides in protonated form, for exampledimethylaminoethyl(meth)acrylamide hydrochloride,dimethylaminopropyl(meth)acrylamide hydrochloride,dimethylaminopropyl(meth)acrylamide hydrosulphate ordimethylaminoethyl(meth)acrylamide hydrosulphate.

Preferred ethylenically unsaturated monomers (α1) containing aquaternized nitrogen are dialkylammonioalkyl(meth)acrylates inquaternized form, for example trimethylammonioethyl(meth)acrylatemethosulphate or dimethylethylammonioethyl(meth)acrylate ethosulphate,and (meth)acrylamidoalkyldialkylamines in quaternized form, for example(meth)acrylamidopropyltrimethylammonium chloride,trimethylammonioethyl(meth)acrylate chloride or(meth)acrylamidopropyltrimethylammonium sulphate.

Preferred monoethylenically unsaturated monomers (α2) copolymerizablewith (α1) are acrylamides and methacrylamides.

Preferred (meth)acrylamides are, in addition to acrylamide andmethacrylamide, alkyl-substituted (meth)acrylamides oraminoalkyl-substituted derivatives of (meth)acrylamide, such asN-methylol(meth)acrylamide, N,N-dimethylamino(meth)acrylamide,dimethyl(meth)acrylamide or diethyl(meth)acrylamide. Possiblevinylamides are, for example, N-vinylamides, N-vinylformamides,N-vinylacetamides, N-vinyl-N-methylacetamides,N-vinyl-N-methylformamides, vinylpyrrolidone. Among these monomers,particular preference is given to acrylamide.

Additionally preferred as monoethylenically unsaturated monomers (α2)copolymerizable with (α1) are water-dispersible monomers. Preferredwater-dispersible monomers are acrylic esters and methacrylic esters,such as methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylateor butyl(meth)acrylate, and also vinyl acetate, styrene and isobutylene.

Crosslinkers (α3) preferred in accordance with the invention arecompounds having at least two ethylenically unsaturated groups withinone molecule (crosslinker class I), compounds having at least twofunctional groups which can react with functional groups of monomers(α1) or (α2) in a condensation reaction (=condensation crosslinkers), inan addition reaction or in a ring-opening reaction (crosslinker classII), compounds which have at least one ethylenically unsaturated groupand at least one functional group which can react with functional groupsof monomers (α1) or (α2) in a condensation reaction, in an additionreaction or in a ring-opening reaction (crosslinker class III), orpolyvalent metal cations (crosslinker class IV). The compounds ofcrosslinker class I achieve crosslinking of the polymers through thefree-radical polymerization of the ethylenically unsaturated groups ofthe crosslinker molecule with the monoethylenically unsaturated monomers(α1) or (α2), while the compounds of the crosslinker class II and thepolyvalent metal cations of crosslinker class IV achieve crosslinking ofthe polymers by a condensation reaction of the functional groups(crosslinker class II) or by electrostatic interaction of the polyvalentmetal cation (crosslinker class IV) with the functional groups ofmonomers (α1) or (α2). In the case of the compounds of crosslinker classIII, there is correspondingly crosslinking of the polymer both byfree-radical polymerization of the ethylenically unsaturated group andby a condensation reaction between the functional group of thecrosslinker and the functional groups of monomers (α1) or (α2).

Preferred compounds of crosslinker class I are poly(meth)acrylic esterswhich are obtained, for example, by the reaction of a polyol, forexample ethylene glycol, propylene glycol, trimethylolpropane,1,6-hexanediol, glycerol, pentaerythritol, polyethylene glycol orpolypropylene glycol, of an amino alcohol, of a polyalkylenepolyamine,for example diethylenetriamine or triethylenetetramine, or of analkoxylated polyol with acrylic acid or methacrylic acid. Preferredcompounds of crosslinker class I are additionally polyvinyl compounds,poly(meth)allyl compounds, (meth)acrylic esters of a monovinyl compoundor (meth)acrylic esters of a mono(meth)allyl compound, preferably of themono(meth)allyl compounds of a polyol or of an amino alcohol. In thiscontext, reference is made to DE 195 43 366 (U.S. Pat. No. 6,087,450 A)and DE 195 43 368 (U.S. Pat. No. 6,143,821 A). The disclosures arehereby incorporated by reference and are thus considered to form part ofthe disclosure.

Examples of compounds of crosslinker class I include alkenyldi(meth)acrylates, for example ethylene glycol di(meth)acrylate,1,3-propylene glycol di(meth)acrylate, 1,4-butylene glycoldi(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanedioldi(meth)acrylate, 1,18-octadecanediol di(meth)acrylate, cyclopentanedioldi(meth)acrylate, neopentyl glycol di(meth)acrylate, methylenedi(meth)acrylate or pentaerythritol di(meth)acrylate,alkenyldi(meth)acrylamides, for example N-methyldi(meth)acrylamide,N,N′-3-methylbutylidenebis(meth)acrylamide,N,N′-(1,2-dihydroxyethylene)bis(meth)acrylamide,N,N′-hexamethylenebis(meth)acrylacrylamide orN,N′-methylenebis(meth)acrylamide, polyalkoxy di(meth)acrylates, forexample diethylene glycol di(meth)acrylate, triethylene glycoldi(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipropyleneglycol di(meth)acrylate, tripropylene glycol di(meth)acrylate ortetrapropylene glycol di(meth)acrylate, bisphenol A di(meth)acrylate,ethoxylated bisphenol A di(meth)acrylate, benzylidene di(meth)acrylate,1,3-di(meth)acryloyloxy-2-propanol, hydroquinone di(meth)acrylate,di(meth)acrylate esters of trimethylolpropane which has preferably beenalkoxylated, preferably ethoxylated, with 1 to 30 mol of alkylene oxideper hydroxyl group, thioethylene glycol di(meth)acrylate, thiopropyleneglycol di(meth)acrylate, thiopolyethylene glycol di(meth)acrylate,thiopolypropylene glycol di(meth)acrylate, divinyl ethers, for example1,4-butanediol divinyl ether, divinyl esters, for example divinyladipate, alkanedienes, for example butadiene or 1,6-hexadiene,divinylbenzene, di(meth)allyl compounds, for example di(meth)allylphthalate or di(meth)allyl succinate, homo- and copolymers ofdi(meth)allyldimethylammonium chloride and homo- and copolymers ofdiethyl(meth)allylaminomethyl(meth)acrylate ammonium chloride,vinyl(meth)acryloyl compounds, for example vinyl(meth)acrylate,(meth)allyl(meth)acryloyl compounds, for example(meth)allyl(meth)acrylate, (meth)allyl(meth)acrylate ethoxylated with 1to 30 mol of ethylene oxide per hydroxyl group, di(meth)allyl esters ofpolycarboxylic acids, for example di(meth)allyl maleate, di(meth)allylfumarate, di(meth)allyl succinate or di(meth)allyl terephthalate,compounds having 3 or more ethylenically unsaturated, free-radicallypolymerizable groups, for example glyceryl tri(meth)acrylate,(meth)acrylate esters of glycerol which has been ethoxylated withpreferably 1 to 30 mol of ethylene oxide per hydroxyl group,trimethylolpropane tri(meth)acrylate, tri(meth)acrylate esters oftrimethylolpropane which has preferably been alkoxylated, preferablyethoxylated, with 1 to 30 mol of alkylene oxide per hydroxyl group,trimethacrylamide, (meth)allylidene di(meth)acrylate,3-allyloxy-1,2-propanediol di(meth)acrylate, tri(meth)allyl cyanurate,tri(meth)allyl isocyanurate, pentaerythritol tetra(meth)acrylate,pentaerythritol tri(meth)acrylate, (meth)acrylic esters ofpentaerythritol ethoxylated with preferably 1 to 30 mol of ethyleneoxide per hydroxyl group, tris(2-hydroxyethyl) isocyanuratetri(meth)acrylate, trivinyl trimellitate, tri(meth)allylamine,di(meth)allylalkylamines, for example di(meth)allylmethylamine,tri(meth)allyl phosphate, tetra(meth)allylethylenediamine,poly(meth)allyl esters, tetra(meth)allyloxyethane ortetra(meth)allylammonium halides.

Preferred compounds of crosslinker class II are compounds which have atleast two functional groups which can react in a condensation reaction(=condensation crosslinkers), in an addition reaction or in aring-opening reaction with the functional groups of monomers (α1) or(α2), preferably with acid groups of monomers (α1). These functionalgroups of the compounds of crosslinker class II are preferably alcohol,amine, aldehyde, glycidyl, isocyanate, carbonate, or epichlorofunctions.

Examples of compounds of crosslinker class II include polyols, forexample ethylene glycol, polyethylene glycols such as diethylene glycol,triethylene glycol and tetraethylene glycol, propylene glycol,polypropylene glycols such as dipropylene glycol, tripropylene glycol ortetrapropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol,2,4-pentanediol, 1,6-hexanediol, 2,5-hexanediol, glycerol, polyglycerol,trimethylolpropane, polyoxypropylene, oxyethylene-oxypropylene blockcopolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fattyacid esters, pentaerythritol, polyvinyl alcohol and sorbitol, aminoalcohols, for example ethanolamine, diethanolamine, triethanolamine orpropanolamine, polyamine compounds, for example ethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine orpentaethylenehexamine, polyglycidyl ether compounds such as ethyleneglycol diglycidyl ether, polyethylene glycol diglycidyl ether, glyceryldiglycidyl ether, glyceryl polyglycidyl ether, pentaerythritylpolyglycidyl ether, propylene glycol diglycidyl ether, polypropyleneglycol diglycidyl ether, neopentyl glycol diglycidyl ether, hexanediolglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitolpolyglycidyl ether, diglycidyl phthalate, adipic acid diglycidyl ether,1,4-phenylenebis(2-oxazoline), glycidol, polyisocyanates, preferablydiisocyanates such as toluene 2,4-diisocyanate and hexamethylenediisocyanate, polyaziridine compounds such as2,2-bishydroxymethylbutanol tris[3-(1-aziridinyl)propionate],1,6-hexamethylenediethyleneurea anddiphenylmethanebis-4,4′-N,N′-diethyleneurea, halogen peroxides, forexample epichloro- and epibromohydrin and α-methylepichlorohydrin,alkylene carbonates such as 1,3-dioxolan-2-one (ethylene carbonate),4-methyl-1,3-dioxolan-2-one (propylene carbonate),4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one,4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one,1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one,4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxolan-2-one,poly-1,3-dioxolan-2-one, polyquaternary amines such as condensationproducts of dimethylamines and epichlorohydrin. Preferred compounds ofcrosslinker class II are additionally polyoxazolines such as1,2-ethylenebisoxazoline, crosslinkers with silane groups, such asγ-glycidoxypropyltrimethoxysilane and γ-aminopropyltrimethoxysilane,oxazolidinones such as 2-oxazolidinone, bis- and poly-2-oxazolidinonesand diglycol silicates.

Preferred compounds of class III include hydroxyl- or amino-containingesters of (meth)acrylic acid, for example 2-hydroxyethyl(meth)acrylateand 2-hydroxypropyl(meth)acrylate, and also hydroxyl- oramino-containing (meth)acrylamides or mono(meth)allyl compounds ofdiols.

The polyvalent metal cations of crosslinker class IV derive preferablyfrom mono- or polyvalent cations, the monovalent especially from alkalimetals such as potassium, sodium, lithium, preference being given tolithium. Preferred divalent cations derive from zinc, beryllium,alkaline earth metals such as magnesium, calcium, strontium, preferencebeing given to magnesium. Further higher-valency cations usable inaccordance with the invention are cations of aluminum, iron, chromium,manganese, titanium, zirconium and other transition metals, and alsodouble salts of such cations or mixtures of the salts mentioned.Preference is given to using aluminum salts and alums and the differenthydrates thereof, for example AlCl₃×6H₂O, NaAl(SO₄)₂×12 H₂O,KAl(SO₄)₂×12 H₂O or Al₂(SO₄)₃×14-18 H₂O. Particular preference is givento using Al₂(SO₄)₃ and hydrates thereof as crosslinkers of crosslinkingclass IV.

The superabsorbent particles used in the process according to theinvention are preferably crosslinked by crosslinkers of the followingcrosslinker classes, or by crosslinkers of the following combinations ofcrosslinker classes: I, II, III, IV, I II, I III, I IV, I II III, I IIIV, I III IV, II III IV, II IV or III IV. The above combinations ofcrosslinker classes are each a preferred embodiment of crosslinkers of asuperabsorbent particle used in the process according to the invention.

Further preferred embodiments of the superabsorbent particles used inthe process according to the invention are polymers which arecrosslinked by any of the aforementioned crosslinkers of crosslinkerclass I. Among these, preference is given to water-soluble crosslinkers.In this context, particular preference is given toN,N′-methylenebisacrylamide, polyethylene glycol di(meth)acrylates,triallylmethylammonium chloride, tetraallylammonium chloride, and allylnonaethylene glycol acrylate prepared with 9 mol of ethylene oxide permole of acrylic acid.

As water-soluble polymers (α4), the superabsorbent particles maycomprise water-soluble polymers, such as partly or fully hydrolyzedpolyvinyl alcohol, polyvinylpyrrolidone, starch or starch derivatives,polyglycols or polyacrylic acid, preferably incorporated in polymerizedform. The molecular weight of these polymers is uncritical provided thatthey are water-soluble. Preferred water-soluble polymers are starch orstarch derivatives or polyvinyl alcohol. The water-soluble polymers,preferably synthetic water-soluble polymers such as polyvinyl alcohol,can also serve as a graft base for the monomers to be polymerized.

The additives (α5) present in the polymers are organic or inorganicsubstances, for example odor binders, especially zeolites orcyclodextrins, skincare substances, surfactants or antioxidants.

The preferred organic additives include cyclodextrins or derivativesthereof, and polysaccharides. Also preferred are cellulose and cellulosederivatives such as CMC, cellulose ethers. Preferred cyclodextrins orcyclodextrin derivatives are those compounds disclosed in DE-A-198 25486 at page 3 line 51 to page 4 line 61 (corresponds to US 2004/157989A1). The aforementioned section of this published patent application ishereby incorporated by reference and is considered to form part of thedisclosure of the present invention. Particularly preferredcyclodextrins are underivatized α-, β-, γ- or δ-cyclodextrins.

The inorganic particulate additives used may be any materials which aretypically used to modify the properties of water-absorbing polymers. Thepreferred inorganic additives include sulphates such as Na₂SO₄,lactates, for instance sodium lactate, silicates, especially frameworksilicates such as zeolites, or silicates which have been obtained bydrying aqueous silica solutions or silica sols, for example thecommercially available products such as precipitated silicas and fumedsilicas, for example Aerosils having a particle size in the range from 5to 50 nm, preferably in the range from 8 to 20 nm, such as “Aerosil 200”from Evonik Industries AG, aluminates, titanium dioxides, zinc oxides,clay materials, and further minerals familiar to those skilled in theart, and also carbonaceous inorganic materials.

Preferred silicates are all natural or synthetic silicates which aredisclosed as silicates in Hollemann and Wiberg, Lehrbuch derAnorganischen Chemie [Inorganic Chemistry], Walter de Gruyter-Verlag,91st-100th edition, 1985, on pages 750 to 783. The aforementionedsection of this textbook is hereby incorporated by reference and isconsidered to form part of the disclosure of the present invention.

Particularly preferred silicates are the zeolites. The zeolites used maybe all synthetic or natural zeolites known to those skilled in the art.Preferred natural zeolites are zeolites from the natrolite group, theharmotone group, the mordenite group, the chabasite group, the faujasitegroup (sodalite group) or the analcite group. Examples of naturalzeolites are analcime, leucite, pollucite, wairakite, bellbergite,bikitaite, boggsite, brewsterite, chabasite, willhendersonite,cowlesite, dachiardite, edingtonite, epistilbite, erionite, faujasite,ferrierite, amicite, garronite, gismondine, gobbinsite, gmelinite,gonnardite, goosecreekite, harmotone, phillipsite, wellsite,clinoptilolite, heulandite, laumontite, levyne, mazzite, merlinoite,montesommaite, mordenite, mesolite, natrolite, scolecite, offretite,paranatrolite, paulingite, perlialite, barrerite, stilbite, stellerite,thomsonite, tschernichite or yugawaralite. Preferred synthetic zeolitesare zeolite A, zeolite X, zeolite Y, zeolite P, or the productABSCENTS®.

The zeolites used may be zeolites of what is called the “intermediate”type, in which the SiO₂/AlO₂ ratio is less than 10; the SiO₂/AlO₂ ratioof these zeolites is more preferably within a range from 2 to 10. Inaddition to these “intermediate” zeolites, it is also possible to usezeolites of the “high” type, which include, for example, the known“molecular sieve” zeolites of the ZSM type, and β-zeolite. These “high”zeolites are preferably characterized by an SiO₂/AlO₂ ratio of at least35, more preferably by an SiO₂/AlO₂ ratio within a range from 200 to500.

The aluminates used are preferably the naturally occurring spinels,especially common spinel, zinc spinel, iron spinel or chromium spinel.

Preferred titanium dioxide is pure titanium dioxide in the rutile,anatase and brookite crystal forms, and also iron-containing titaniumdioxides, for example ilmenite, calcium-containing titanium dioxidessuch as titanite or perovskite.

Preferred clay materials are those disclosed as clay materials inHollemann and Wiberg, Lehrbuch der Anorganischen Chemie, Walter deGruyter-Verlag, 91st-100th edition, 1985, on pages 783 to 785.Particularly the aforementioned section of this textbook is herebyincorporated by reference and is considered to form part of thedisclosure of the present invention. Particularly preferred claymaterials are kaolinite, illite, halloysite, montmorillonite and talc.

Further inorganic fines preferred in accordance with the invention arethe metal salts of the mono-, oligo- and polyphosphoric acids. Amongthese, preference is given especially to the hydrates, particularpreference being given to the mono- to decahydrates and trihydrates.Useful metals include especially alkali metals and alkaline earthmetals, preference being given to the alkaline earth metals. Amongthese, Mg and Ca are preferred and Mg is particularly preferred. In thecontext of phosphates, phosphoric acids and metal compounds thereof,reference is made to Hollemann and Wiberg, Lehrbuch der AnorganischenChemie, Walter de Gruyter-Verlag, 91st-100th edition, 1985, on pages 651to 669. The aforementioned section of this textbook is herebyincorporated by reference and is considered to form part of thedisclosure of the present invention.

Preferred carbonaceous but nonorganic additives are those pure carbonswhich are mentioned as graphites in Hollemann and Wiberg, Lehrbuch derAnorganischen Chemie, Walter de Gruyter-Verlag, 91st-100th edition,1985, on pages 705 to 708. The aforementioned section of this textbookis hereby incorporated by reference and is considered to form part ofthe disclosure of the present invention. Particularly preferredgraphites are synthetic graphites, for example coke, pyrographite,activated carbon or carbon black.

The water-absorbing polymers obtained in the process according to theinvention are preferably obtainable by first preparing a hydrogelpolymer in particulate form from the aforementioned monomers andcrosslinkers. This starting material for the water-absorbing polymers isproduced, for example, by bulk polymerization which is preferablyeffected in kneading reactors such as extruders, solutionpolymerization, spray polymerization, inverse emulsion polymerization orinverse suspension polymerization. Preference is given to performing thesolution polymerization in water as a solvent. The solutionpolymerization can be effected continuously or batchwise. The prior artdiscloses a wide spectrum of possible variations with regard to reactionconditions, such as temperatures, type and amount of the initiators, andof the reaction solution. Typical processes are described in thefollowing patents: U.S. Pat. No. 4,286,082, DE 27 06 135, U.S. Pat. No.4,076,663, DE 35 03 458, DE 40 20 780, DE 42 44 548, DE 43 23 001, DE 4333 056, DE 44 18 818. The disclosures are hereby incorporated byreference and are thus considered to form part of the disclosure.

The initiators used to initiate the polymerization may be all initiatorswhich form free radicals under the polymerization conditions and aretypically used in the production of superabsorbents. These includethermal initiators, redox initiators and photoinitiators, which areactivated by means of high-energy radiation. The polymerizationinitiators may be present dissolved or dispersed in a solution ofinventive monomers. Preference is given to the use of water-solubleinitiators.

Useful thermal initiators include all compounds which decompose to freeradicals when heated and are known to those skilled in the art.Particular preference is given to thermal polymerization initiatorshaving a half-life of less than 10 seconds, further preferably of lessthan 5 seconds at less than 180° C., further preferably at less than140° C. Peroxides, hydroperoxides, hydrogen peroxide, persulphates andazo compounds are particularly preferred thermal polymerizationinitiators. In some cases, it is advantageous to use mixtures ofdifferent thermal polymerization initiators. Among these mixtures,preference is given to those of hydrogen peroxide and sodiumperoxodisulphate or potassium peroxodisulphate, which can be used in anyconceivable ratio. Suitable organic peroxides are preferablyacetylacetone peroxide, methyl ethyl ketone peroxide, benzoyl peroxide,lauroyl peroxide, acetyl peroxide, capryl peroxide, isopropylperoxydicarbonate, 2-ethylhexyl peroxydicarbonate, t-butylhydroperoxide, cumene hydroperoxide, t-amyl perpivalate, t-butylperpivalate, t-butyl perneohexanoate, t-butyl isobutyrate, t-butylper-2-ethylhexenoate, t-butyl perisononanoate, t-butyl permaleate,t-butyl perbenzoate, t-butyl 3,5,5-trimethylhexanoate and amylperneodecanoate. Further preferred thermal polymerization initiatorsare: azo compounds such as azobisisobutyronitrile,azobisdimethylvaleronitrile,2,2′-azobis(2-amidinopropane)dihydrochloride, azobisamidinopropanedihydrochloride, 2,2′-azobis(N,N-dimethylene)isobutyramidinedihydrochloride, 2-(carbamoylazo)isobutyronitrile and4,4′-azobis(4-cyanovaleric acid). The compounds mentioned are used incustomary amounts, preferably within a range from 0.01 to 5 mol %,preferably from 0.1 to 2 mol %, based in each case on the amount of themonomers to be polymerized.

The redox initiators comprise, as the oxidizing component, at least oneof the above-specified per compounds, and, as the reducing component,preferably ascorbic acid, glucose, sorbose, mannose, ammoniumhydrogensulphite, sulphate, thiosulphate, hyposulphite or sulphide,alkali metal hydrogensulphite, sulphate, thiosulphate, hyposulphite orsulphide, metal salts such as iron(II) ions or silver ions, or sodiumhydroxymethylsulphoxylate. The reducing component used in the redoxinitiator is preferably ascorbic acid or sodium pyrosulphite. Based onthe amount of monomers used in the polymerization, 1×10⁻⁵ to 1 mol % ofthe reducing component of the redox initiator and 1×10⁻⁵ to 5 mol % ofthe oxidizing component of the redox initiator are used. Instead of theoxidizing component of the redox initiator, or in addition thereto, itis possible to use one or more, preferably water-soluble, azo compounds.

If the polymerization is triggered by the action of high-energyradiation, it is customary to use what are called photoinitiators as theinitiator. These may be, for example, what are called α-splitters,H-abstracting systems, or else azides. Examples of such initiators arebenzophenone derivatives such as Michler's ketone, phenanthrenederivatives, fluorene derivatives, anthraquinone derivatives,thioxanthone derivatives, coumarin derivatives, benzoin ethers andderivatives thereof, azo compounds such as the abovementionedfree-radical formers, substituted hexaarylbisimidazoles or acylphosphineoxides. Examples of azides are: 2-(N,N-dimethylamino)ethyl4-azidocinnamate, 2-(N,N-dimethylamino)ethyl 4-azidonaphthyl ketone,2-(N,N-dimethylamino)ethyl 4-azidobenzoate, 5-azido-1-naphthyl2′-(N,N-dimethylamino)ethyl sulphone,N-(4-sulphonylazidophenyl)maleimide, N-acetyl-4-sulphonylazidoaniline,4-sulphonylazidoaniline, 4-azidoaniline, 4-azidophenacyl bromide,p-azidobenzoic acid, 2,6-bis(p-azidobenzylidene)cyclohexanone and2,6-bis(p-azido-benzylidene)-4-methylcyclohexanone. If they are used,the photoinitiators are employed typically in amounts of 0.01 to 5% byweight, based on the monomers to be polymerized.

Preference is given in accordance with the invention to using aninitiator system consisting of hydrogen peroxide, sodiumperoxodisulphate and ascorbic acid. In general, the polymerization isinitiated with the initiators within a temperature range from 0° C. to90° C.

The polymerization reaction can be triggered by one initiator or by aplurality of interacting initiators. In addition, the polymerization canbe performed in such a way that one or more redox initiators are firstadded. Later in the polymerization, thermal initiators orphotoinitiators are then applied additionally, and the polymerizationreaction in the case of photoinitiators is then initiated by the actionof high-energy radiation. The reverse sequence, i.e. the initialinitiation of the reaction by means of high-energy radiation andphotoinitiators or thermal initiators and initiation of thepolymerization by means of one or more redox initiators later in thepolymerization, is also conceivable.

In order to convert the hydrogel polymers thus obtained to a particulateform, they can first, after they have been comminuted or coarselydivided, be dried at a temperature within a range from 20 to 300° C.,preferably within a range from 50 to 250° C. and more preferably withina range from 100 to 200° C., down to a water content of less than 40% byweight, preferably of less than 20% by weight and further preferably ofless than 10% by weight, based in each case on the total weight of thehydrogel polymer. The drying is effected preferably in ovens or driersknown to those skilled in the art, for example in belt driers, stageddriers, rotary tube ovens, fluidized bed driers, pan driers, paddledriers or infrared driers.

According to the present invention, the milling or grinding of the driedpolymer is preferably effected by dry grinding, preferably by drygrinding in a hammer mill, a pinned disc mill, a ball mill or a rollmill. In a further version of the present invention, the dried polymercan also be milled or ground by the combinations of two or more of theabove-described mills.

In a preferred embodiment of the processes according to the invention,the water-absorbing polymers obtained are particles having an innerregion and a surface region bordering the inner region. The surfaceregion has a different chemical composition from the inner region, ordiffers from the inner region in a physical property. Physicalproperties in which the inner region differs from the surface regionare, for example, the charge density or the degree of crosslinking.

These water-absorbing polymers having an inner region and a surfaceregion bordering the inner region are preferably obtainable bypost-crosslinking reactive groups close to the surface of the particlesof the particulate hydrogel polymer (PC). This post-crosslinking can beeffected thermally, photochemically or chemically.

Preferred post-crosslinkers are the compounds of crosslinker classes IIand IV mentioned in connection with the crosslinkers (α3).

Among these compounds, particularly preferred post-crosslinkers arediethylene glycol, triethylene glycol, polyethylene glycol, glycerol,polyglycerol, propylene glycol, diethanolamine, triethanolamine,polyoxypropylene, oxyethylene-oxypropylene block copolymers, sorbitanfatty acid esters, polyoxyethylene sorbitan fatty acid esters,trimethylolpropane, pentaerythritol, polyvinyl alcohol, sorbitol,1,3-dioxolan-2-one (ethylene carbonate), 4-methyl-1,3-dioxolan-2-one(propylene carbonate), 4,5-dimethyl-1,3-dioxolan-2-one,4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one,4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one,4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one,1,3-dioxolan-2-one, poly-1,3-dioxolan-2-one.

Particular preference is given to using ethylene carbonate as thepost-crosslinker.

Preferred embodiments of the water-absorbing polymers are those whichare post-cross-linked by crosslinkers of the following crosslinkerclasses or by crosslinkers of the following combinations of crosslinkerclasses: II, IV and II IV.

The post-crosslinker is preferably used in an amount within a range from0.01 to 30% by weight, more preferably in an amount within a range from0.1 to 20% by weight and further preferably in an amount within a rangefrom 0.3 to 5% by weight, based in each case on the weight of thesuperabsorbent polymers in the post-crosslinking.

It is likewise preferred that the post-crosslinking is effected bycontacting a solvent comprising preferably water, water-miscible organicsolvents, for instance methanol or ethanol or mixtures of at least twothereof, and the post-crosslinker with the outer region of the hydrogelpolymer particles. The hydrogel polymer particles are then typicallyheated to a temperature within a range from 30 to 300° C., morepreferably within a range from 100 to 200° C. to complete the surface-or post-crosslinking reaction and remove excess water or other solventused as a carrier. The contacting is preferably effected by spraying themixture consisting of post-crosslinker and solvent onto the hydrogelpolymer particles and then mixing the hydrogel polymer particlescontacted with the mixture. The post-crosslinker is present in themixture preferably in an amount within a range from 0.01 to 20% byweight, more preferably in an amount within a range from 0.1 to 10% byweight, based on the total weight of the mixture. It is additionallypreferred that contact with the hydrogel polymer particles is effectedin an amount within a range from 0.01 to 50% by weight, more preferablyin an amount within a range from 0.1 to 30% by weight, based in eachcase on the weight of the hydrogel polymer particles.

Useful condensation reactions preferably include the formation of ester,amide, imide or urethane bonds, and preference being given to theformation of ester bonds.

The inventive hydrogel polymers and/or water-absorbing polymers canadditionally be admixed with further additives including those that actas effect substances. Additives may be added to the water-absorbingpolymer at any stage of the production process, including into themonomer, the wet gel or the dried polymer before or afterpost-crosslinking. If the additive is sensitive to heat, abrasion orother steps of the manufacturing process, it may be preferable to beadded after the post-crosslinking step as one of the last productionsteps. Or it may be that ease of addition, or activity or desired effectof the additive is improved. Such additions after post-crosslinking aregenerally referred to as finishing or finishing treatments.

Preferred additives are additionally release agents, for instanceinorganic or organic pulverulent release agents. These release agentsare preferably used in amounts within a range from 0 to 2% by weight,more preferably within a range from 0.1 to 1.5% by weight, based on theweight of the hydrogel polymer and/or of the water-absorbing polymer.Preferred release agents are wood flour, pulp fibers, powdered bark,cellulose powder, mineral fillers such as perlite, synthetic fillerssuch as nylon powder, rayon powder, diatomaceous earth, bentonite,kaolin, zeolites, talc, loam, ash, carbon dust, magnesium silicates,fertilizers or mixtures of the substances. Finely divided fumed silica,as sold under the Aerosil trade name by Evonik Degussa, is preferred.

In a further preferred embodiment of the process according to theinvention, the hydrogel polymer particles and/or the water-absorbingpolymer particles are contacted with an effect substance additive, forexample a polysugar, a polyphenolic compound, for example hydrolysabletannins or a compound containing silicon-oxygen, microbe inhibitingsubstances, enzyme inhibitors, odor absorbers, odor maskers,anti-perspirants and the like, or a mixture of at least two effectsubstances based thereon. The effect substance can be added either insolid form (powder) or in dissolved form with a solvent, the effectsubstance being added not earlier than after process step iii). In thecontext of the present invention, an effect substance additive isunderstood to mean a substance which serves for odor inhibition.

According to the invention, polysugars by which the person skilled inthe art understands those from the group of the familiar starches andderivatives thereof, celluloses and derivatives thereof, cyclodextrins.Cyclodextrins are preferably understood to mean α-cyclodextrin,β-cyclodextrin, γ-cyclodextrin or mixtures of these cyclodextrins.

Preferred compounds containing silicon-oxygen are zeolites. The zeolitesused may be all synthetic or natural zeolites known to those skilled inthe art. Preferred natural zeolites are zeolites from the natrolitegroup, the harmotone group, the mordenite group, the chabasite group,the faujasite group (sodalite group) or the analcite group. Examples ofnatural zeolites are analcime, leucite, pollucite, wairakite,bellbergite, bikitaite, boggsite, brewsterite, chabazite,willhendersonite, cowlesite, dachiardite, edingtonite, epistilbite,erionite, faujasite, ferrierite, amicite, garronite, gismondine,gobbinsite, gmelinite, gonnardite, goosecreekite, harmotome,phillipsite, wellsite, clinoptilolite, heulandite, laumontite, levyne,mazzite, merlinoite, montesommaite, mordenite, mesolite, natrolite,scolecite, offretite, paranatrolite, paulingite, perlialite, barrerite,stilbite, stellerite, thomsonite, tschernichite or yugawaralite.Preferred synthetic zeolites are zeolite A, zeolite X, zeolite Y,zeolite P, or the product ABSCENTS®.

The cations present in the zeolites used in the process according to theinvention are preferably alkali metal cations such as Li⁺, Na⁺, K⁺, Rb⁺,Cs⁺ or Fr⁺ and/or alkaline earth metal cations such as Mg²⁺, Ca²⁺, Sr²⁺or Ba²⁺.

The zeolites used may be zeolites of what is called the “intermediate”type, in which the SiO₂/AlO₂ ratio is less than 10; the SiO₂/AlO₂ ratioof these zeolites is more preferably within a range from 2 to 10. Inaddition to these “intermediate” zeolites, it is also possible to usezeolites of the “high” type, which include, for example, the known“molecular sieve” zeolites of the ZSM type, and beta-zeolite. These“high” zeolites are preferably characterized by an SiO₂/AlO₂ ratio of atleast 35, more preferably by an SiO₂/AlO₂ ratio within a range from 200to 500.

The zeolites are preferably used in the form of particles with a meanparticle size within a range from 1 to 500 μm, more preferably within arange from 2 to 200 μm and further preferably within a range from 5 to100 μm.

The effect substances are used in the processes according to theinvention preferably in an amount within a range from 0.1 to 50% byweight, more preferably within a range from 1 to 40% by weight andfurther preferably in an amount within a range from 5 to 30% by weight,based in each case on the weight of the hydrogel polymer particlesand/or water-absorbing polymer particles.

Preferred microbe-inhibiting substances are in principle all substancesactive against Gram-positive bacteria, for example 4-hydroxybenzoic acidand salts and esters thereof,N-(4-chlorophenyl)-N′-(3,4-dichlorophenyl)urea,2,4,4′-trichloro-2′-hydroxydiphenyl ether (triclosan),4-chloro-3,5-dimethylphenol, 2,2′-methylenebis(6-bromo-4-chlorophenol),3-methyl-4-(1-methylethyl)phenol, 2-benzyl-4-chlorophenol,3-(4-chlorophenoxy)-1,2-propanediol, 3-iodo-2-propynyl butylcarbamate,chlorhexidine, 3,4,4′-trichlorocarbonilide (TTC), antibacterialfragrances, thymol, thyme oil, eugenol, clove oil, menthol, mint oil,famesol, phenoxyethanol, glyceryl monocaprate, glyceryl monocaprylate,glyceryl monolaurate (GML), diglyceryl monocaprate (DMC),N-alkylsalicylamides, for example N-n-octylsalicylamide orN-n-decylsalicylamide.

Suitable enzyme inhibitors are, for example, esterase inhibitors. Theseare preferably trialkyl citrates such as trimethyl citrate, tripropylcitrate, triisopropyl citrate, tributyl citrate and especially triethylcitrate (Hydagen TM CAT, Cognis GmbH, Düsseldorf, Germany). Thesubstances inhibit enzyme activity and as a result reduce odorformation. Further substances useful as esterase inhibitors are sterolsulphates or phosphates, for example lanosterol sulphate or phosphate,cholesterol sulphate or phosphate, campesterol sulphate or phosphate,stigmasterol sulphate or phosphate and sitosterol sulphate or phosphate,dicarboxylic acids and esters thereof, for example glutaric acid,monoethyl glutarate, diethyl glutarate, adipic acid, monoethyl adipate,diethyl adipate, malonic acid and diethyl malonate, hydroxycarboxylicacids and esters thereof, for example citric acid, malic acid, tartaricacid or diethyl tartrate, and zinc glycinate.

Suitable odor absorbers are substances which can absorb andsubstantially retain odor-forming compounds. They lower the partialpressure of the individual components and thus also reduce the rate ofspread thereof. It is important that perfumes must remain unimpaired.Odor absorbers generally have no effect against bacteria. They contain,for example, as the main constituent, a complex zinc salt of ricinoleicacid or specific, substantially odor-neutral fragrances known to theperson skilled in the art as “fixatives”, for example extracts oflabdanum or styrax or particular abietic acid derivatives. The functionof odor maskers is fulfilled by odorants or perfume oils which, inaddition to their function as odor maskers, impart their particularfragrance note to the deodorants. Examples of perfume oils includemixtures of natural and synthetic odorants. Natural odorants areextracts of flowers, stems and leaves, fruits, fruit skins, roots,woods, herbs and grasses, needles and twigs, and also resins andbalsams. Additionally useful are animal raw materials, for example civetand castoreum. Typical synthetic odorant compounds are products of theester, ether, aldehyde, ketone, alcohol and hydrocarbon type. Odorantcompounds of the ester type are, for example, benzyl acetate,p-tert-butylcyclohexyl acetate, linalyl acetate, phenylethyl acetate,linalyl benzoate, benzyl formate, allyl cyclohexylpropionate, styrallylpropionate and benzyl salicylate. The ethers include, for example,benzyl ethyl ether; the aldehydes include, for example, the linearalkanals having 8 to 18 carbon atoms, citral, citronellal,citronellyloxyacetaldehyde, cyclamen aldehyde, hydroxycitronellal,lilial and bourgeonal; the ketones include, for example, the ionones andmethyl cedryl ketone; the alcohols include anethole, citronellol,eugenol, isoeugenol, geraniol, linalool, phenylethyl alcohol andterpineol; the hydrocarbons include principally the terpenes andbalsams. Preference is given, however, to using mixtures of differentodorants which together produce a pleasing fragrance note. Suitableperfume oils are also essential oils of relatively low volatility whichare usually used as aroma components, for example sage oil, camomileoil, clove oil, melissa oil, mint oil, cinnamon leaf oil, lime blossomoil, juniperberry oil, vetiver oil, olibanum oil, galbanum oil, labdanumoil and lavender oil. Preference is given to using bergamot oil,dihydromyrcenol, lilial, lyral, citronellol, phenylethyl alcohol,alpha-hexylcinnamaldehyde, geraniol, benzylacetone, cyclamen aldehyde,linalool, Boisambrene Forte, ambroxan, indole, Hedione, Sandelice, lemonoil, mandarin oil, orange oil, allyl amyl glycolate, cyclovertal,lavender oil, clary sage oil, beta-damascone, geranium oil bourbon,cyclohexyl salicylate, Vertofix Coeur, Iso-E-Super, Fixolide NP,Evernyl, iraldein gamma, phenylacetic acid, geranyl acetate, benzylacetate, rose oxide, Romilat, Irotyl and Floramat, alone or in mixtures.

Antiperspirants reduce the formation of perspiration by influencing theactivity of the eccrine sweat glands, and thus counteract underarmwetness and body odor. Suitable astringent active antiperspirantingredients are in particular salts of aluminum, zirconium or zinc. Suchsuitable antihydrotically active ingredients are, for example, aluminumchloride, aluminum chlorohydrate, aluminum dichlorohydrate, aluminumsesquichlorohydrate and the complexes thereof, for example withpropylene 1,2-glycol, aluminum hydroxyallantoinate, aluminum chloridetartrate, aluminum zirconium trichlorohydrate, aluminum zirconiumtetrachlorohydrate, aluminum zirconium pentachlorohydrate and thecomplexes thereof, for example with amino acids such as glycine.

Examples of further additives in the context of the present inventioninclude anticaking compounds, for example kaolin, Aerosils®, Sipernats®,and the like, insoluble inorganic additives based on silicon, forexample silicas or silica sols, aluminum salts such as aluminum sulphateor aluminum lactate, surfactants, viscosity modifiers or the like, whichare applied to the surface of the polymer particles or else react withthe free polymer chains of the polymer particle.

Suitable apparatus for mixing or spraying is any which allowshomogeneous distribution of a solution, powder, suspension or dispersionon or with the hydrogel polymer particles ( ) or water-absorbingpolymers. Examples are Lödige mixers (manufactured by Gebrüder LödigeMaschinenbau GmbH), Gericke multi-flux mixers (manufactured by GerickeGmbH), DRAIS mixers (manufactured by DRAIS GmbH SpezialmaschinenfabrikMannheim), Hosokawa mixers (Hosokawa Mokron Co., Ltd.), Ruberg mixers(manufactured by Gebr. Ruberg GmbH & Co. KG Nieheim), Hüttlin coaters(manufactured by BWI Hüttlin GmbH Steinen), fluidized bed driers orspray granulators from AMMAG (manufactured by AMMAG Gunskirchen,Austria) or Heinen (manufactured by A. Heinen AG Anlagenbau Varel),Patterson-Kelly mixers, NARA paddle mixers, screw mixers, pan mixers,fluidized bed driers or Schugi mixers. For contacting in a fluidizedbed, it is possible to employ all fluidized bed processes which areknown to those skilled in the art and appear to be suitable. Forexample, it is possible to use a fluidized bed coater.

A further contribution to the solution of the problem stated at theoutset is made by the process for preparing a water-absorbing polymer,comprising the process steps of

-   -   (i) mixing    -   (α1) 0.1 to 99.999% by weight, preferably 20 to 98.99% by weight        and more preferably 30 to 98.95% by weight of polymerizable,        ethylenically unsaturated monomers containing acid groups, or        salts thereof, or polymerizable, ethylenically unsaturated        monomers including a protonated or quaternized nitrogen, or        mixtures thereof, particular preference being given to mixtures        including at least ethylenically unsaturated monomers containing        acid groups, preferably acrylic acid,    -   (α2) 0 to 70% by weight, preferably 1 to 60% by weight and more        preferably 1 to 40% by weight of polymerizable, ethylenically        unsaturated monomers copolymerizable with (α1),    -   (α3) 0.001 to 10% by weight, preferably 0.01 to 7% by weight and        more preferably 0.05 to 5% by weight of one or more        crosslinkers,    -   (α4) 0 to 30% by weight, preferably 1 to 20% by weight and more        preferably 5 to 10% by weight of water-soluble polymers,    -   (α5) 0-90% by weight, preferably 2.5-75% by weight and more        preferably 10-60% by weight of water, and    -   (α6) 0-20% by weight, preferably 0-10% by weight and more        preferably 0.1-8% by weight of one or more additives, where the        sum of the weights of (α1) to (α6) is 100% by weight,    -   (ii) free-radical polymerization with crosslinking to form a        water-insoluble, aqueous untreated hydrogel polymer,    -   (iii) comminuting the hydrogel polymer,    -   (iv) drying the hydrogel polymer,    -   (v) grinding and sieving the hydrogel polymer to size,    -   (vi) surface post-crosslinking the ground and sieved hydrogel        polymer and    -   (vii) finishing the water-absorbing polymer,    -   wherein    -   the water-absorbing polymer has been treated with 0.0001 to 3%        by weight, preferably 0.002 to 2% by weight and more preferably        0.007 to 1.8% by weight of a peroxo compound, based on the        acrylic acid, after the polymerization, are added in steps (iii)        to (vii).

In a further preferred embodiment, the peroxo compound is used in anamount of 0.0001 to 1.5% by weight, based on the acrylic acid, after thepolymerization.

In a further embodiment, in accordance with the invention, the peroxocompound is selected those from the group of organic and inorganicperoxo compounds.

In a further preferred embodiment, in accordance with the invention, analkali metal salt of an inorganic peroxo compound is used.

In a further preferred embodiment, in accordance with the invention, theperoxo compound is added in steps (iii) to (vii), explicitly in step(iii), (iv), (v), (vi) and/or (vii).

In a further particularly preferred embodiment, in accordance with theinvention, the peroxo compound is added in step (vii).

In one further embodiment the process for preparing a water-absorbingpolymer comprises the process steps of

-   -   (i) mixing    -   (α1) 0.1 to 99.999% by weight, preferably 20 to 98.99% by weight        and more preferably 30 to 98.95% by weight of polymerizable,        ethylenically unsaturated monomers containing acid groups, or        salts thereof, or polymerizable, ethylenically unsaturated        monomers including a protonated or quaternized nitrogen, or        mixtures thereof, particular preference being given to mixtures        including at least ethylenically unsaturated monomers containing        acid groups, preferably acrylic acid,    -   (α2) 0 to 70% by weight, preferably 1 to 60% by weight and more        preferably 1 to 40% by weight of polymerizable, ethylenically        unsaturated monomers copolymerizable with (α1),    -   (α3) 0.001 to 10% by weight, preferably 0.01 to 7% by weight and        more preferably 0.05 to 5% by weight of one or more        crosslinkers,    -   (α4) 0 to 30% by weight, preferably 1 to 20% by weight and more        preferably 5 to 10% by weight of water-soluble polymers,    -   (α5) 0-90% by weight, preferably 2.5-75% by weight and more        preferably 10-60% by weight of water, and    -   (α6) 0-20% by weight, preferably 0-10% by weight and more        preferably 0.1-8% by weight of one or more additives, where the        sum of the weights of (α1) to (α6) is 100% by weight,    -   (ii) free-radical polymerization with crosslinking to form a        water-insoluble, aqueous untreated hydrogel polymer,    -   (iii) comminuting the hydrogel polymer,    -   (iv) drying the hydrogel polymer,    -   (v) grinding and sieving the hydrogel polymer to size,    -   (vi) surface post-crosslinking the ground and sieved hydrogel        polymer and    -   (vii) drying and finishing the water-absorbing polymer,    -   wherein    -   the water-absorbing polymer has been treated with 0.0001 to 3%        by weight, preferably 0.002 to 2% by weight and more preferably        0.007 to 1.8% by weight of a peroxo compound, based on the        acrylic acid, after the polymerization, are added in steps (iii)        to (vii).

The improved odor control of the water-absorbing polymer of the presentinvention is shown in the following examples, and tests, directed to theprevention of the formation of ammonia as determined by theDetermination of Ammonia (NH₃) release (Proteus mirabilis) Test, and thereduction of organic molecules as determined by the Determination of theReduction in Organic Molecule Odor Test. SAP give some prevention of theformation of ammonia. In particular, the following reference SAP sampleshows 6-7 hrin the prevention of the formation of ammonia. In accordancewith the present invention, the prevention of the formation of ammoniain accordance with the Determination of Ammonia (NH₃) release (Proteusmirabilis) Test is more than 8 hours, or ranges from 12 to 35 hr, orranges from 15 to 30 hr, or from 17 to 25 hr. or from 18 to 22 hr; andthe reduction of organic molecules has been reduced based on themolecule. As shown in the reference sample, the % reduction after 16 hr.in the organic molecules including pyrrole, furfuryl mercaptan,(S)-(+)-carvone, indole, trimethylamine, and dimethyl disulfide is 0%.In accordance with the present invention, the % reduction in organicmolecules in accordance with the Determination of the Reduction inOrganic Molecule Odor Test are as follows:

-   -   a % reduction ranging from 50 to 99.9%, or from 60 to 99.9%, or        from 70 to 99.9%, or from 80 to 99.9%, or from 90 to 99.9%, or        from 95 to 99.8%, of pyrrole; and/or    -   a % reduction ranging from 50 to 99.9%, or from 60 to 99.9%, or        from 70 to 99.9%, or from 80 to 99.9%, or from 90 to 99.9%, or        from 95 to 99.8%, of furfuryl mercaptan; and/or    -   a % reduction ranging from 50 to 99.9%, or from 60 to 99.9%, or        from 70 to 99.9%, or from 80 to 99.9%, or from 90 to 99.9%, or        from 95 to 99.8%, of (S)-(+)-carvone; and/or    -   a % reduction ranging from 50 to 99.9%, or from 60 to 99.9%, or        from 70 to 99.9%, or from 80 to 99.9%, or from 90 to 99.9%, or        from 95 to 99.8%, of indole; and/or    -   a % reduction ranging from 10 to 30%, or from 15 to 27%, of        trimethylamine; and/or    -   a % reduction ranging from 50 to 99.9%, or from 60 to 99.9%, or        from 70 to 99.9%, or from 80 to 99.9%, or from 85 to 96%, of        dimethyl disulfide.

As shown above and in the following examples, the present inventionprovides a superabsorbent polymer including a single odor controltreatment, wherein the resulting superabsorbent polymer has superiorammonia odor control and reduces not just control one type of organicmolecule odor, but a wide variety of types of organic molecule odorsthat usually require different treatments.

A further contribution to the solution of the problems described at theoutset is made by a composite including the inventive water-absorbingpolymers or the hydrogel polymers, or the water-absorbing polymers orhydrogel polymers obtainable by the processes according to theinvention, and a substrate. It is preferable that the inventivewater-absorbing polymers or hydrogel polymers and the substrate arebonded in a fixed manner to one another. Preferred substrates are filmsof polymers, for example of polyethylene, polypropylene or polyamide,metals, nonwovens, fluff, tissues, fabrics, natural or synthetic fibers,or foams. It is additionally preferred in accordance with the inventionthat the composite comprises at least one region which includeswater-absorbing polymers or hydrogel polymers in an amount in the rangefrom about 15 to 100% by weight, preferably about 30 to 100% by weight,more preferably from about 50 to 99.99% by weight, further preferablyfrom about 60 to 99.99% by weight and even further preferably from about70 to 99% by weight, based in each case on the total weight of theregion of the composite in question, this region preferably having asize of at least 0.01 cm³, preferably at least 0.1 cm³ and mostpreferably at least 0.5 cm³.

A further contribution to the solution of at least one of the problemsstated at the outset is made by a process for producing a composite,wherein the inventive water-absorbing polymers or the superabsorbentsobtainable by the process according to the invention and a substrate andoptionally an additive are contacted with one another. The substratesused are preferably those substrates which have already been mentionedabove in connection with the inventive composite.

A contribution to the solution of at least one of the problems stated atthe outset is also made by a composite obtainable by the processdescribed above, this composite preferably having the same properties asthe above-described inventive composite.

A further contribution to the solution of at least one of the problemsstated at the outset is made by chemical products including theinventive water-absorbing polymers or hydrogel polymers or an inventivecomposite. Preferred chemical products are especially foams, moldings,fibers, foils, films, cables, sealing materials, liquid-absorbinghygiene articles, especially diapers, nappies and sanitary towels,carriers for plant growth or fungal growth regulators or plantprotection active ingredients, additives for building materials,packaging materials or soil additives.

The use of the inventive water-absorbing polymers or of the inventivecomposite in chemical products, preferably in the aforementionedchemical products, especially in hygiene articles such as nappies orsanitary towels, and the use of the water-absorbing polymer particles ascarriers for plant growth or fungal growth regulators or plantprotection active ingredients also make a contribution to theachievement of at least one of the problems stated at the outset. In thecase of use as a carrier for plant growth or fungal growth regulators orplant protection active ingredients, it is preferred that the plantgrowth or fungal growth regulators or plant protection activeingredients can be released over a period controlled by the carrier.

Test Methods

Unless stated otherwise hereinafter, the measurements conducted hereinare according to ERT methods. “ERT” stands for EDANA Recommended Testand “EDANA” for European Disposables and Nonwovens Association. All testmethods are in principle, unless stated otherwise, conducted at anambient temperature of 23±2° C. and a relative air humidity of 50±10%.

Particle Size Distribution (PSD)

The particle size distribution of the water-absorbing polymer particlesis determined analogously to EDANA recommended test method No. WSP220.3-10 “Particle Size Distribution”.

Centrifuge Retention Capacity (CRC)

The centrifuge retention capacity was determined by EDANA (EuropeanDisposables and Nonwovens Association) recommended test method No. WSP241.3-1.0, “Centrifuge retention capacity”.

Absorption Against a Pressure of 0.7 Psi (AAP)

The absorption under pressure was determined as the AAP (AbsorptionAgainst Pressure) to WSP 242.3-10 on the overall particle fraction.Accordingly, 0.90 g of the test substance (sieved off between 150 and850 μm) was weighed into a test cylinder of internal diameter 60.0 mmwith a sieve base (400 mesh) (concentration: 0.032 g/cm²) anddistributed homogeneously. A cylindrical weight (50 g/cm²=0.7 psi) withan external diameter of 59.2 mm was placed onto the test substance.Filter plates were placed into a plastic dish, and were covered with afilter paper. The plastic dish was filled with 0.9% NaCl solution untilthe liquid level concluded with the upper edge of the filter plates.Subsequently, the prepared test units were placed onto the filterplates. After a swelling time of 60 minutes, the test units werewithdrawn and the weight was removed. The amount of liquid absorbed wasdetermined gravimetrically and converted to the amount absorbed per 1gram of test substance.

Determination of Ammonia (NH₃) Release (Proteus mirabilis):

Proteus mirabilis was grown on a slanted Caso agar at 37° C. overnight.The bacteria culture was washed off with 5 ml of synthetic urine (25 g/lurea, 9 g/l sodium chloride, 5 g/l glucose, 4 g/l potassium sulphate,2.5 g/l ammonium sulphate, 0.7 g/l calcium acetate, 0.7 g/l magnesiumsulphate×7 H₂O, 0.5 g/l yeast extract, 5 g/l meat extract, 5 g/lpeptone). The microbe count of the synthetic urine was adjusted suchthat an initial microbe count of about 10⁵ CFU/ml urine was present. Ineach case 33 ml of the synthetic urine with added bacteria weretransferred into Erlenmeyer flasks, and 1 g of superabsorbent was added.The vessels were closed with a rubber stopper, through the hole of whichwas passed a Dräger diffusion tube (ammonia 20/a-D), and incubated at37° C. in an incubator. The ammonia released was measured in ppm×h.

Determination of the Reduction in Organic Molecule Odor

By Solid Phase Microextration (SPME)—Gas Chromatography (GC)

This test determines the odor reduction of six different organicmalodors, representing six different classes of chemical compounds.

0.50 g of the superabsorbent to be determined are weighed accuratelyinto a 200 ml Erlenmeyer flask and admixed with 11.0 g of a mixtureconsisting of 100 ng/ml dimethyl trisulphide, 0.5 ng/ml pyrrole, 50ng/ml furfuryl mercaptan, 0.5 ng/ml (S)-(+)-carvone, 0.5 ng/ml indoleand 13 000 ng/ml trimethylamine in a 0.9% by weight aqueous NaClsolution. The flask is sealed with a threaded adapter having a septumand stored in a climate-controlled cabinet at 37° C. for 16 h toestablish equilibrium in the vapour space. Now the SPME phase isintroduced into the vapor space for 30 min and then injected directlyinto a gas chromatograph, for desorption and malodor amount analysis.The decrease or the reduction in concentration of the odorant isdetermined in relation to the corresponding reference sample in %.Instrument Parameters:

Flask 200 ml Erlenmeyer flask with NS 29 = volume 255 ml with threadedadapter and septum SPME Phase Supelco Carboxen/PDMS-black GC columnRESTEK Corp. RTX-50, 30 m, 0.53 GC Hewlett Packard 5890 Carrier Gas HeHeating rates 7 min. 30° C. 10° C./min. to 180° C. 30° C./min. to 250°C.

EXAMPLES

The examples which follow serve for further illustration of theinvention, but without restricting it thereto.

For the inventive examples which follow, a defined particle sizedistribution (PSD) was used (150 μm to 850 μm).

The term “SX” as used in the description is understood to mean thethermal surface post-crosslinking of the precursor (PC). The precursorcorresponds to the hydrogel polymer obtained after the first drying andmilling, with the aforementioned particle distribution.

Description of the Production of the SAP Samples

Polymer Material (Powder A)

A monomer solution consisting of 300 g of acrylic acid, neutralized toan extent of 60 mol % with 200.2 g of 50% NaOH, 474.8 g of water, 1.62 gof polyethylene glycol-300 diacrylate, 0.89 g of monoallyl polyethyleneglycol-450 monoacrylate was freed of the dissolved oxygen by degassingwith nitrogen and cooled to the start temperature of about 4° C. Afterthe start temperature had been attained, the initiator solutionconsisting of 0.3 g of sodium peroxodisulphate in 10 g of water, 0.07 gof 35% hydrogen peroxide solution in 10 g of water and 0.015 g ofascorbic acid in 2 g of water was added. An exothermic polymerizationreaction took place. The adiabatic end temperature was about 100° C. Thehydrogel formed was comminuted with a laboratory meat grinder (5 mm dieplate) and the comminuted sample was dried at 170° C. for 90 minutes ina laboratory air circulation drying cabinet. The dried polymer was firstcoarsely crushed and then ground by means of an SM100 cutting millhaving an aperture size of 2 mm, and sieved to a powder having aparticle size of 150 to 850 μm. 100 g of the powder were coated with asolution of 1.0 g of ethylene carbonate and 3.0 g of deionized water.This was done by applying the solution with a syringe (0.45 mm cannula)to the polymer powder present in the mixer. The coated powder was thenheated in a drying cabinet at 170° C. over a period of 90 minutes.

Example 1, Reference Sample

The reference sample used was powder A without further additionaltreatment.

Example 2

100 g of powder A were admixed with 0.5 g of potassiumperoxomonosulphate triple salt (Caro's acid) and homogenized on anoverhead agitator for about 2 h.

Example 3

100 g of powder A were admixed with 1.0 g of potassiumperoxomonosulphate triple salt and homogenized on an overhead agitatorfor about 2 h.

Ammonia Odor Control:

Sample Retention AAP 0.7 NH₃ odor Reference [g/g] psi [g/g] control [hr]Reference sample, Example 1 30.2 21.2 6-7 Example 2 31.0 20.4 18-20Example 3 31.2 20.3 20-22

As can be seen by the above results, the inventive odor-controlsuperabsorbent polymer is surprisingly effective in preventing theformation of ammonia for 18 to 22 hours, while maintaining excellentabsorption properties compared to the reference example where ammonia isgenerated after only 6 or 7 hours.

Organic Molecules—Odor Control:

Reduction in Reduction in Reduction in pyrrole [%] furfuryl mercaptan(S)-(+)- carvone compared to [%] compared to [%] compared Samplereference after reference after to reference after Reference 16 hr 16 hr16 hr Reference sample, 0 0 0 example 1 Inventive Example 99.2 95.5 97.92 Inventive Example 99.2 96.7 97.5 3

Reduction in Reduction in Reduction in indole [%] trimethylamine [%]dimethyl disulfide Sample compared to compared to [%] compared toReference reference after 16 hr reference after 16 hr reference after 16hr Reference 0 0 0 sample, example 1 Inventive 95.2 18.3 93.9 Example 2Inventive 98.8 23.9 89.3 Example 3

As clearly demonstrated by the above results, the inventive odor-controlsuperabsorbent is effective in controlling malodors not only fromammonia, but also those from organic molecules. The malordous organicsubstances used: pyrrole, furfuryl mercaptan, (S)-(+)-carvone, indole,trimethylamine and dimethyl disulfilde are six different well knownmalodors, representing six different chemical classes of compounds. Theinventive absorbents surprisingly are capable of eliminating up to 99%of these odors in the headspace above the absorbent.

Examples 2 and 3 were repeated with equivalent amounts of differentsalts of peroxomonosulphate and peroxodisulphate and sulpho monoperacid.All peroxo compounds tested showed excellent properties in controllingmalodors and achieved similar results as the once listed in the tablesabove.

Additionally the peroxo compound potassium peroxomonosulphate triplesalt was tested with various different SAP samples supplemental to theabove tests with powder A. All tested SAP particles based on monomers indifferent concentrations, different internal crosslinkers, differentpost-crosslinkers, and different production conditions which weretreated according to Example 2 or Example 3 showed outstanding resultsin preventing the formation of ammonia for 18 to 22 hours and incontrolling malodors not only from ammonia, but also those from organicmolecules.

The invention claimed is:
 1. A process for preparing water-absorbingpolymers, comprising the process steps of (i) mixing (α1) 0.1 to 99.999%by weight of polymerized, ethylenically unsaturated monomers bearingacid groups, or salts of polymerized, ethylenically unsaturated monomersbearing acid groups, or polymerized, ethylenically unsaturated monomerscomprising a protonated nitrogen, polymerized, ethylenically unsaturatedmonomers comprising a quaternized nitrogen, or mixtures thereof; (α2) 0to 69.999% by weight of polymerizable, ethylenically unsaturatedmonomers copolymerizable with (α1), (α3) 0.001 to 10% by weight of oneor more crosslinkers, (α4) 0 to 30% by weight of water-soluble polymers,(α5) 0-90% by weight of water, and (α6) 0-20% by weight of one or moreadditives where the sum of the weights of (α1) to (α6) is 100% byweight, (ii) free-radical polymerization with crosslinking to form awater-insoluble, aqueous untreated hydrogel polymer, (iii) comminutingthe hydrogel polymer, (iv) drying the hydrogel polymer, (v) grinding andsieving the hydrogel polymer to size, (vi) surface post-crosslinking theground and sieved hydrogel polymer and (vii) finishing thewater-absorbing polymer, wherein the water-absorbing polymer has beentreated with 0.0001 to 3% by weight of a peroxo compound based on (α1),after the polymerization; and the peroxo compound is selected from thegroup consisting of alkali metal or alkaline earth metalperoxomonosulphate, peroxodisulphate, sulpho monoperacid andperoxomonosulphate triple salt.
 2. The process according to claim 1,wherein the water-absorbing polymer has been treated with 0.0001 to 1.5%by weight of a peroxo compound based on (α1), after the polymerization.3. The process according to claim 1, characterized in that the peroxocompound is added in steps (iii), (iv), (v), (vi) and/or (vii).
 4. Theprocess according to claim 1, wherein the peroxo compound is added instep (vii).
 5. The process according to claim 1, wherein (α1) is 0.1 to99.999% by weight of polymerized, ethylenically unsaturated monomersbearing acid groups.
 6. The process according to claim 1, wherein theperoxomonosulfate triple salt is potassium peroxymonosulfate.